In 1982, the fixed combination of pyrimethamine and sulfadoxine (Fansidar®) became available in the United States, and was recommended for use in travelers at risk of acquiring chloroquine-resistant Plasmodium falciparum. Prior to that time, no reports of severe cutaneous reactions had appeared in the medical literature despite widespread use for more than 8 years in both Europe and malarious areas of the developing world. In the fall of 1984, the Centers for Disease Control received reports of 4 cases of toxic epidermal necrolysis (including 3 fatalities) among Americans who had used pyrimethamine-sulfadoxine (PYR/SDX) for the prevention of malaria. Subsequent investigation into severe cutaneous reactions associated with the use of this drug by American travelers detected 24 cases of erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis. Twenty-three of the 24 patients concurrently used chloroquine. Seven patients died. No risk factors in the development of these reactions other than the use of PYR/SDX could be identified. Among American travelers, we estimate that these reactions occur in 1 per 5,000–8,000 users, and that fatal reactions occur in 1 per 11,000–25,000 users. This higher than expected incidence necessitates that the use of PYR/SDX for the prevention of malaria be reconsidered. In the United States it is now recommended that the routine weekly use of the drug be reserved for those travelers at highest risk of acquiring chloroquine-resistant P. falciparum, when alternate prophylactic regimens are not deemed appropriate.

Between 1981 and 1983, in vivo and in vitro studies were conducted in Haiti to assess the responsiveness of Plasmodium falciparum to chloroquine. The standard tests successfully performed included 92 WHO standardized in vivo field tests and 160 in vitro tests (64 macrotests, 33 microtests, and 63 48-hr tests). No clearcut evidence of chloroquine resistance was detected. In 3 in vivo and 5 in vitro tests, a decreased susceptibility to the drug was suggested, but these isolated findings failed to be corroborated by parallel alternate tests. In addition, during the initial trial of an alternate monitoring system, 339 simplified 7-day in vivo tests were successfully performed, with no suggestion of resistance detected. This simplified 7-day in vivo test potentially represents an efficient low cost method for monitoring drug resistance in many developing countries.

In 1984 the government of Malawi instituted a program to reduce malaria mortality and morbidity in children <5 years of age as a part of the Combatting Childhood Communicable Diseases (CCCD) program. To define the appropriate malaria therapy regimen, investigators used a quality assurance design in a simplified 7-day in vivo drug response study with follow-up observations on day 2 (D2), D3, and D7 after the initial day of the study (D0). The efficacy of oral chloroquine was assessed in 224 children who were enrolled at 6 sites, 2 in each of the 3 administrative regions of Malawi. Parasitological failure, defined as failure of parasitemia to decrease by 75% of the value by D3 or presence of any detectable parasitemia on D7, ranged from 41%–65% following administration of chloroquine 25 mg (base)/kg. However, only 8% of children who were parasitemic on D7 were febrile or judged to be ill. Considering these therapeutic results and the higher cost and limited availability of alternative therapies, chloroquine 25 mg/kg therapy was adopted as the primary therapy for malaria.

The Indochina I/CDC strain of Plasmodium falciparum was linearly passaged in squirrel monkeys (Saimiri sciureus) of 3 phenotypes. Splenectomized monkeys of Guyanan and Peruvian type developed high density parasitemias, but considerably lower than the mean peak parasitemia (> 106/mm3) in Bolivian phenotype squirrel monkeys. Spleenintact Bolivian and Peruvian squirrel monkeys all developed potentially lethal infections after linear passage of parasites from Saimiri and Aotus. For the evaluation of induced immunity to P. falciparum, the Indochina I/CDC strain in Saimiri will be a valuable model system.

Transport of nutrients into animal cells is driven by transmembrane gradient of Na+ across the plasma membrane. The protozoan malaria parasite, Plasmodium falciparum, however, grows within the host human erythrocytes, in which the cytoplasmic concentration of Na+ is maintained low by the membrane Na+, K+-ATPase. Our experiments show that human erythrocytes enriched with Na+ by treatment with ouabain (an inhibitor of the ATPase) will support the growth of P. falciparum in culture.

The circumsporozoite (CS) proteins of strains of the Plasmodium cynomolgi complex have been examined using antisporozoite monoclonal antibodies (Mab) in various immunologic assays. We found extensive antigenic diversity in the repeating immunodominant epitope of the CS proteins of the various strains. Based on the antigenicity and the electrophoretic mobility of their CS protein, the 11 strains that we examined can be placed in 7 distinct groups. Our data also indicate homology between the immunodominant repetitive epitopes of the CS proteins of the Berok strain of P. cynomologi and the human malaria parasite P. vivax.

Grace's insect medium, supplemented with 20% (v/v) heat-inactivated fetal bovine serum (FBS) and 15% defibrinated pooled rabbit blood is statistically shown to be more sensitive than modified NNN medium (P < 0.05), Grace's insect medium with 20% (v/v) and Grace's insect medium with 30% (v/v) FBS (P <0.01) for in vitro primary isolation of promastigotes of Leishmania donovani donovani from cultures of bone marrow aspirates. This medium has been found to be especially useful for parasitological diagnosis of untreated cases of visceral leishmaniasis and for cases where microscopic examination of bone marrow aspirates has been negative for Leishman-Donovan bodies.

Two cases of cutaneous leishmaniasis of 12 and 27 months duration are described. These were acquired in Saudi Arabia and Ethiopia. The cases were treated with 8 and 4 weeks of ketoconazole, respectively, with an excellent response.

Administration of cyclosporin A (CyA) to mice prior to infection and at weekly intervals during the infection with Giardia muris resulted in an increase in cyst output and a delay of the elimination phase of the infection. A short term treatment (4 days) of infected mice with CyA induced a significantly higher cyst release after treatment. CyA did not affect the ability of immune mice to resist reinfection. Our findings indicate that CyA has compromised immunological control of the primary Giardia infection, but not the ability of the immune host to resist reinfection. We propose that the use of immunosuppressive drugs may be a contributing factor in transmission of giardiasis.

A 43-year-old Filipino male was admitted to a Manila hospital with a 1 month history of epigastric pain and fever, and was found to have a palpable epigastric mass. Computerized tomography revealed a large hepatic abscess which serologically was shown to be amebic. Chemotherapy resulted in clinical cure and an initial reduction in size of the liver abscess. However, resolution of the abscess cavity did not occur, and on closed needle aspiration, 80 cc of characteristic amebic pus was recovered. Parasitological cure without complete repair of the abscess cavity itself raises questions concerning the potential danger of clinically silent residua and the role of therapeutic aspiration in the management of amebic liver abscesses.

The reactivity of peripheral blood mononuclear cells (PBMN) from 62 chagasic patients to antigens prepared with different Trypanosoma cruzi strains and clones belonging to different zymodemes was evaluated by the incorporation of 3H-thymidine into DNA. Standardization of experimental conditions was carried out by establishing the proper antigen concentration (15–20 µg protein), the adequate period of time (5–6 days) and the best cell concentration (300,000/well). Individual analysis of 62 patients showed 2 distinct patterns of cellular response. One group of patients (32%) had low cellular responses to all antigens tested while the remaining patients had high response to at least 1 of the antigens. No relationship of the immune responsiveness to the patients' clinical forms could be established. In addition, the PBMN response to different strain and clone antigens was not statistically significant. Thus, it appears that the cellular response induced by any particular clone or strain represents an expression of the stimulation of their common antigenic make-up.

Rhodnius neivai was as efficient as Rhodnius prolixus and Rhodnius robustus in transmitting by bite a Colombian strain of Trypanosoma rangeli following its inoculation into the hemocoel. Under conditions of the study the strain of T. rangeli had a high and constant infectivity to the salivary glands of R. prolixus, its natural vector in Colombia. Six species of Triatoma and Dipetalogaster maximus likewise inoculated did not develop metatrypomastigotes in the salivary glands. Of the 12 known species of Rhodnius, R. neivai is the eighth to be demonstrated as an anterior station vector of T. rangeli.

Twelve young adult captivity-born tamarin monkeys (Saguinus fuscicollis) were each exposed to 150 cercariae of Schistosoma mansoni (KEB strain): 6 by the percutaneous (pc) and 6 by the subcutaneous (sc) route. The prepatent period, as determined by eggs in the feces, was 34–39 days for both groups. Weekly quantitative fecal examinations revealed that although both groups actively passed eggs for as long as the duration of the experiment (18 months), the sc group excreted a significantly higher number of eggs/gram/day in the feces than did the pc group. Eggs recovered from the feces of both groups were viable: they hatched and the miracidia invaded snails which subsequently yielded infective cercariae. A significantly greater number of worms was recovered from tamarins infected by the sc route as compared to those with pc infections, and large numbers of eggs were found in affected organs of the sc group. Chronically infected tamarins with high tissue egg loads developed focal granulomatous nodules along the serosal walls of the small intestines, which in some cases, apparently had budded off to lie free in the abdominal cavity. Hepatic granulomas from animals with acute infections were significantly larger than those from chronically infected monkeys.

Our results strongly suggest the presence of a skin barrier to infection in the tamarin monkey, and that if this barrier is bypassed, the tamarin can serve as a permissive host for S. mansoni. The small body size of this monkey (<400 g) is an obvious reason for the establishment of the tamarin monkey as a laboratory nonhuman primate model for human schistosomiasis mansoni.

Yields of parasites during the period of worm migration from the lungs to the portal circulation were measured in S. mansoni-infected Fischer rats passively immunized with protective serum from twice-infected donor rats. Two effects of protective serum were observed in recipient rats relative to normal serum recipients: yields of schistosomula from lungs were higher and yields of (immature) worms from the portal circulation were lower throughout the period analyzed. Histopathological analysis of lung tissue confirmed the presence of greater numbers of schistosomula in lungs of passively immunized rats. In addition, the percent of lung schistosomula involved in all categories of inflammatory reactions was greater in recipients of protective rat serum.

The kinetics of accumulation of worms perfused from the portal circulation of normal and passively immunized rats indicate that in the latter group a smaller fraction of worms successfully migrates to the portal circulation. These findings support the hypothesis that protective activity of the serum prevents a portion of worms from successfully completing migration from the lung to the portal circulation.

Forty-six monoclonal antibodies were produced against the preacetabular gland secretions of Schistosoma mansoni cercariae by two different immunization protocols. These antibodies were of both the IgG and the IgM classes. One IgM monoclonal antibody (Ia4D6) was further characterized. It was specific to the cercarial stage by ELISA and showed specific binding to the 30,000 Mr proteinase in crude cercarial secretions by Western blot analysis. Preincubation of this antibody with purified cercarial proteinase resulted in inhibition of proteolytic activity, and it mediated complement-dependent cytotoxicity to cercariae in vitro. Immunoperoxidase staining of cercariae localized this antibody to vesicles visible within the preacetabular glands and their secretory ducts, and to secreted material. ELISA and Western blot analysis also showed that sera from infected mice and patients with schistosomiasis reacted with the cercarial proteinase. These studies demonstrate that a proteinase secreted into the host by invading cercariae is immunogenic and provide a monoclonal antibody probe for further characterization of its structure and function.

Introduction of the fluorescent group lissamine rhodamine B into the surface of schistosomula of S. mansoni was achieved by brief incubation of the worms with liposomes carrying the lipid bound fluorophore in their bilayers. The liposomers were made of egg lecithin (PC) and lissamine-phosphatidylethanolamine (lissamine-PE). The lissamine groups could be directly detected on the parasite membrane by observation of the single worms under a fluorescent microscope. The fluorescent marker was employed to measure the lateral diffusion coefficient (D) of lipids in the schistosomular membrane and as a surface marker during the isolation of the schistosomula surface membrane.

The purpose of this study was to determine the ultrastructural localization of a major schistosome circulating antigen — the circulating anodic antigen (CAA) — in the digestive tract of various life cycle stages of Schistosoma mansoni. The presence of CAA was determined by an indirect gold-labeling procedure using CAA-specific monoclonal antibodies. In cercariae, gold label was found in the cytoplasm and in the surface coat of the gut epithelium. A minimal amount of gold particles was also observed in the esophagus epithelium, but this was limited to the luminal surface coat and located proximally to the gut. In 3½-week-old worms and in adult male and female worms CAA was demonstrable in the Golgi apparatus, in cytoplasmic vesicles, and in the luminal surface coat of the gut epithelium. As determined in the adult worms, CAA-positive lysosome-like bodies were only encountered in the most caudal quarter of the gut. In the gut lumen CAA was associated with host white blood cells and with a thick layer of finely granular, moderately electrondense material covering the gut epithelium. The esophagus of these worms did not show CAA reactivity. These results definitely prove that CAA is a gut-specific antigen produced by various life cycle stages of S. mansoni, from the cercarial stage on.

We evaluated the potential value of a cloned sequence of genomic DNA of Brugia malayi as a species-specific probe. Clone pBm 15 reacted with all stages of 8 different geographic isolates of B. malayi and cross-hybridized with microfilariae of B. timori. It did not hybridize with Wuchereria bancrofti or with B. pahangi, W. kalimantani, Dirofilaria repens, Breinlia booliati or Cardiofilaria species, animal filariids that can be sympatric with B. malayi. P32-labeled clone pBm 15 correctly identified mosquitoes infected even with 1 infective larva of B. malayi. This specific DNA probe should be an invaluable tool to monitor control programs of Brugian filariasis.

We used counterimmunoelectrophoresis (CIEP) with rabbit antibodies to Dirofilaria immitis and Brugia malayi to detect soluble filarial antigen in sera collected in a Wuchereria bancrofti-endemic area in South India. Filarial antigen was detected in 38 of 38 sera from microfilaremic patients, 3 of 48 sera from amicrofilaremic patients with lymphatic pathology, and 3 of 5 sera from former microfilaria carriers with negative blood examinations 6 months or more after diethylcarbamazine therapy. One of 32 endemic control sera, 0 of 35 nonendemic sera, and 0 of 20 B. malayi sera were positive. Antigenemia was equally detectable in sera collected at night or during the day (when microfilariae are absent from the blood). Parasite antigen was also detected in the urine of patients with positive serum tests. Antibodies to circulating filarial antigen (also detected by CIEP) were absent in all but 2 antigen-positive sera but present in 22 of 45 antigen-negative sera from clinical filariasis patients and in 9 of 31 antigen-negative sera from endemic controls. Parasite antigen detection by CIEP appears to be a sensitive, specific, and practical diagnostic test for active W. bancrofti infection.